A steam generating container A heated by a heat source includes: a water evaporation chamber into which water is supplied by a water supply device; a leading opening to lead steam from the water evaporation chamber, and ejection openings ejecting steam led through the leading opening into a heating chamber containing food. A buffer chamber connecting through the leading opening and with the ejection openings is provided between the water evaporation chamber and the heating chamber. Even when bumping water enters the buffer chamber through the leading opening, the bumping water having entered flows inside the buffer chamber. Thus, the bumping water is hardly ejected into the heating chamber through the ejection openings.
